温度对大叶桃花心木(Swietenia macrophylla King)幼苗叶片的光合影响

本文研究了大叶桃花心木（Swietenia macrophylla King）一年生幼苗在经过夜温处理后的光响应曲线和在饱和光强下的CO2反应曲线.结果表明:在大气CO2浓度下,叶片的最佳光合作用温度在25-31℃之间,而在饱和CO2浓度下为31-35℃.在25℃以下光合速率开始降低,主要是由于羧化效率的降低,而当温度超过31℃时,光合速率下降,是因为羧化效率的降低和呼吸速率的增加.CO2浓度对光合的促进作用在低温下受到抑制,这意味着未来在CO2浓度增高的情况下,高浓度的CO2对热带常绿植物光合的促进在冬天低温情况下表现不十分明显.图4参23.     

大叶桃花心木抽提物对菜青虫的杀虫活性研究

将楝科植物大叶桃花心木叶的甲醇抽提物用氯仿萃取，所得萃取物对菜青虫进行生物活性测试．结果表明，萃取物有高效的毒杀与生长发育抑制作用．1％药液浸叶饲喂法处理试虫，5d后试虫的生长比率为24．5％，7d后校正死亡率达92．5％，拒食率为94．4％，但触杀作用则为中等活性；而点滴法处理的LC_(50)为2．43％．以植物性杀虫剂川楝素与印楝油做药效比较，表明萃取物的拒食与生长发育抑制活性高于印楝油．     

The Impact of Hardwood Line-Planting on Tree and Amphibian Diversity in a Secondary Subtropical Wet Forest of Southeast Puerto Rico

The impact on tree and amphibian diversity of line-planting of tropical hardwoods—mahogany (Swietenia macrophylla × S. mahagoni) and mahoe (Hibiscus elatus)—was studied in a secondary subtropical wet forest of Puerto Rico. Common coqui (Eleutherodactylus coqui) and melodious coqui (E. wightmanae) are the most frequent frog species; forest coqui (E. portoricensis) is less abundant. Although relative abundance means were slightly greater in the undisturbed forest and during the wet season, differences were not statistically significant suggesting that line-planting did not significantly affect amphibian diversity. The line-planted areas had a slightly higher, but not statistically significant diversity, richness, and evenness of tree species than the unplanted forest. Multi-response permutation procedure (MRPP) showed statistically significant community composition differences between line-planting and control plot trees (T = ?5.89, A = .86; p < .001). But mean similarity among plots in both the line-planted and control plots was relatively low at less than 50% of shared species, indicating high diversity of vegetation in the overall forest area. Canopy cover by tree species greater than 3 cm in dbh was much higher in the undisturbed forest but this difference may be reduced as the young line-planted hardwoods mature. Forest enrichment through line-planting of valuable timber species in secondary subtropical wet forest does not significantly affect tree diversity.     

桃花心木与思茅松混交幼林生长特征研究

对种植于云南省孟连县的桃花心木与思茅松混交幼林的生长指标进行了调查分析,结果表明:定植1.5年后,桃花心木与思茅松1∶1及1∶22种混交比例的混交幼林内,桃花心木的高径生长率均高于思茅松。桃花心木种植初期具有极快的生长速度,是值得云南热区大力推广种植的一个珍贵用材树种。     

Planting mahogany in canopy gaps created by commercial harvesting

Attempts at natural forest management of mahogany (Swietenia macrophylla King) have so far met with limited success, whilst many plantations are beset by the shoot borer Hypsipyla spp. In this paper we present preliminary results of an approach to enrichment planting that aims to balance economic returns (rapid growth and good silvicultural form) with intervention costs and changes to forest structure. Mahogany seedlings were planted in gaps created by selective timber harvesting and that ranged in vertical projected area from 91 to 542 m² (mean = 257 m²). Seedlings grew within the matrix of gap regrowth, with limited control of competing vegetation. Sixty-one percent of seedlings had survived by 4.4 years (equivalent to an annual mortality rate of 10.5% year⁻¹), and had reached a mean height of 4.5 m. Stocking levels of mahogany were similar to that of naturally regenerated commercial species in unplanted gaps of the same age, but mahogany seedlings were significantly taller. The incidence of shoot borer attack on mahogany stems was relatively low (54.7%), but, more importantly, most damaged stems (58%) responded by producing a single replacement leader. The cost of the proposed methodology (US$ 94 per gap over 4.4 years) was low compared to the high value of mahogany timber relative to other species in the forest. The implications of planting mahogany in gaps for forest management and the potential benefits to conservation of the species are considered.     

向天果提取物对肾性高血压动物试验研究

通过2K1C法制作肾性高血压(RH)大鼠模型,研究向天果提取物(SME)对肾性高血压大鼠的降压和靶器官保护等治疗作用。将造模成功的大鼠随机分为模型组、阳性组(25mg/kg卡托普利)、SME高剂量组(500mg/kg)、SME低剂量组(250mg/kg)。给药8周后,血液生化测定肾功能指标,并采用ELISA测定肾素-血管紧张素-醛固酮系统(RAAS)活性。取右肾进行组织切片,HE染色,组织学观察。结果表明,与模型组相比,SME能显著降低RH大鼠收缩压(P<0.01)。与模型组相比,SME高、低剂量组明显降低RH大鼠RAAS水平(P<0.01)。各治疗组对RH大鼠肾脏损伤有不同程度的改善。说明向天果提取物有降压、保护肾脏的作用,其机制可能与抑制RAAS兴奋,抑制血管收缩,以及水钠重吸收有关。     

Community Forestry in the Mayan Biosphere Reserve in Guatemala

Abstract

We present an initial assessment of a community forestry program in the Bethel Cooperative in Northern Guatemala, which is located within the Mayan Biosphere Reserve, part of the Man in the Biosphere Program. Implementing the polycyclic felling system, 20 forest plots will be harvested in succession, one every 20 years. Within the harvest areas and at control sites, permanent monitoring plots have been established to study tree growth and natural regeneration. An average incremental growth rate was determined to be 0.68 cm/yr and was independent of whether or not harvest occurred, but was not independent of the commercial classification of the trees. Size class structure revealed a mixed-aged stand for all commercial categories that was minimally impacted by harvest. Natural regeneration of saplings and small trees may be affected by harvest and could impose long-term limits on the production of marketable trees. However, current cutting practices, size class structure, and conservative estimates of tree growth indicate that consistent harvests can be sustained well into the future. Community income from and participation in forestry-related activities were significant. Finding new markets, enhancing the marketability of new species, and developing non-timber forest resource trade and related activities will be crucial for the success of this program.     

高温热处理对桃花心木化学性质的影响

热处理是木材加工行业中常用的处理手段之一,可有效提升木材尺寸稳定性及具有防生物侵蚀能力,但在一定程度上也会降低木材的力学性能.热处理导致木材材性变化的根本原因是木材组分含量及其分子结构在热量作用下发生了变化.笔者探索了不同热处理温度下(150,165,180,195和210℃)桃花心木材的化学组分变化.结果表明:经热处...     

Swietenine: A potential oral hypoglycemic from Swietenia macrophylla seed

Swietenine, a tetranortriterpenoid, was isolated from the Swietenia macrophylla seeds. The in vivo hypoglycemic activity was evaluated against neonatal-streptozotocin induced type 2 diabetic rats. Oral administration of swietenine at 25 and 50 mg/kg body weight per day to diabetic rats was found to possess significant dose dependant hypoglycemic and hypolipidemic activity in type 2 diabetic rats.     

Red Oak in Southern New England and Big-Leaf Mahogany in the Yucatán Peninsula: Can Mixed-Species Forests Be Sustainably Managed for Single-Species Production?

Complex mixed-species forests are the focus of conservation efforts that seek to maintain native biodiversity. However, much of this forestland is privately owned and is managed for timber income as well as for conservation. Management of these high-diversity forests is particularly difficult when only one tree species produces the majority of high-value timber. We examined the past and current management of two regions which have those characteristics: Massachusetts, USA, with red oak (Quercus rubra L.) as the key timber species, and Quintana Roo, México, with big-leaf mahogany (Swietenia macrophylla King) as the most valuable species. These regions have different ecological characteristics, forest ownership types, landowner income, and importance of timber in total income, yet the silvicultural approach (low-intensity selective cutting) is surprisingly similar, and is generally failing to provide the conditions needed for regeneration and growth of key species. In both situations, the reluctance to harvest low-value species and interest in minimizing forest disturbance complicates management. Successful balance of timber harvest and forest conservation may be an important factor in preventing conversion of these lands to agriculture or residential development, but socioeconomic conditions (property tax policies and landowner affluence) play an important part in the outcome.